A nuclear reactor pressure vessel installation is disclosed by the U.S. Keller Application Ser. No. 367,955, filed June 7, 1973, as comprising a pressurized-water reactor pressure vessel surrounded by the wall of a biological shield which forms a space between it and the vessel. Vertical steel beams, each formed in part by two vertical steel channels, are circumferentially interspaced at relatively large distances around the periphery of the reactor pressure vessel to support the latter, but while forming vertical passages of extensive cross-sectional area to which the pressurized-water coolant can escape upwardly with little resistance, in the event the pressure vessel ruptures.
With this relatively large circumferential interspacing of the vertical beams, the wall of the pressure vessel remains substantially unsupported throughout each area between the interspaced beams. However, upwardly extending spaces are formed having the advantage that they may be used for the upward flow of air coolant between the pressure vessel wall and the concrete wall to protect the latter against excessive heating.